CI test failures

[felinira]

For some reason test_file_rust2rust_deprecated and test_file_rust2rust seem to fail sometimes. There must be some race condition (or server issue?) that causes this behaviour.

Example:
https://github.com/magic-wormhole/magic-wormhole.rs/actions/runs/8039989930/job/21957566544#step:13:1377

---- core::test::test_file_rust2rust_deprecated stdout ----
Error: Key confirmation failed. If you didn't mistype the code, this is a sign of an attacker guessing passwords. Please try again some time later.

Location:
    src/core/test.rs:194:32

---- core::test::test_send_many stdout ----
Error: Error with the rendezvous server connection

Caused by:
    Received error message from server: crowded

Location:
    src/core/test.rs:406:13

[felinira]

Duplicate of #187